In the manufacturer of various semiconductor devices, wire bonding techniques are often used to connect components in the devices (e.g., die to substrate/leadframe bonding; die to die bonding, etc.). For example, wire bonds (aka wire loops) are often used to provide electrical interconnection between (1) die pads of a semiconductor die and (2) contacts (e.g., leads) of a substrate (e.g., a leadframe) upon which the semiconductor die is mounted. An exemplary conventional wire bonding operation involves (1) bonding a first bond to a first bonding location on a die (e.g., using ball bonding), (2) extending a wire toward a second bonding location on a leadframe, (3) bonding the end of the extended wire to the second bonding location, and (4) cutting the wire. In such ball bonding, an electronic flame off (i.e., EFO) wand or the like is typically used to form a “ball” (aka a free air ball) at the end of the wire.
Often, gold wire (which is substantially non-reactive with oxygen) is used in wire bonding processes; however, in certain applications, more reactive metals (e.g., copper, silver, palladium, aluminum, etc.) are used. These more reactive metals may react, for example, in the presence of oxygen and form oxides/oxidation on the wires (and/or wire ends or tails) which are undesirable for wire bonding.
In view of such potential oxidation, certain wire bonding systems include subsystems for providing a cover gas to the end of a wire during formation of the ball by the EFO wand. For example, U.S. Pat. No. 6,234,376, which is incorporated by reference in its entirety, discloses such a system. Unfortunately, such cover gas subsystems do not protect the entire wire (or the entire duration of the wire bonding process) from potential oxidation, and as such, oxidation problems in wire looping with reactive metals still exists.
Other attempts at reducing oxidation in the processing of semiconductor devices include U.S. Pat. No. 5,265,788 (titled “Bonding Machine with Oxidation Preventive Means”); U.S. Pat. No. 6,866,182 (titled “Apparatus and Method to Prevent Oxidation of Electronic Devices”); and U.S. Pat. No. 7,182,793 (titled “System for Reducing Oxidation of Electronic Devices”). Certain of these conventional systems use a clamp in conjunction with other devices in order to reduce the potential for oxidation; however, such systems tend to be complex and may be costly as additional components are added to the wire bonding system.
Thus, it would be desirable to provide a method and apparatus for reducing oxidation in wire bonding.